linux-kernel - Re: [PATCH v1 4/5] [media] stm32-dcmi: set default format at open()

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Date:   Fri, 4 Aug 2017 14:00:05 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Hugues Fruchet <hugues.fruchet@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Yannick Fertre <yannick.fertre@...com>
Subject: Re: [PATCH v1 4/5] [media] stm32-dcmi: set default format at open()

On 28/07/17 12:05, Hugues Fruchet wrote:
> Ensure that we start with default pixel format and resolution
> when opening a new instance.

Why? The format is persistent in V4L2 and (re)opening the video device
shouldn't change the format.

Suppose you use v4l2-ctl to set up a format. E.g. v4l2-ctl -v width=320,height-240.
Now run v4l2-ctl -V to get the format and with this code it would suddenly be
back to the default!

You set up the default format in the dcmi_graph_notify_complete, but after that
it is only changed if userspace explicitly requests it.

Regards,

	Hans

> 
> Signed-off-by: Hugues Fruchet <hugues.fruchet@...com>
> ---
>  drivers/media/platform/stm32/stm32-dcmi.c | 49 ++++++++++++++++++-------------
>  1 file changed, 28 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
> index 4733d1f..2be56b6 100644
> --- a/drivers/media/platform/stm32/stm32-dcmi.c
> +++ b/drivers/media/platform/stm32/stm32-dcmi.c
> @@ -890,6 +890,28 @@ static int dcmi_enum_frameintervals(struct file *file, void *fh,
>  	return 0;
>  }
>  
> +static int dcmi_set_default_fmt(struct stm32_dcmi *dcmi)
> +{
> +	struct v4l2_format f = {
> +		.type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
> +		.fmt.pix = {
> +			.width		= CIF_WIDTH,
> +			.height		= CIF_HEIGHT,
> +			.field		= V4L2_FIELD_NONE,
> +			.pixelformat	= dcmi->sd_formats[0]->fourcc,
> +		},
> +	};
> +	int ret;
> +
> +	ret = dcmi_try_fmt(dcmi, &f, NULL);
> +	if (ret)
> +		return ret;
> +	dcmi->sd_format = dcmi->sd_formats[0];
> +	dcmi->fmt = f;
> +
> +	return 0;
> +}
> +
>  static const struct of_device_id stm32_dcmi_of_match[] = {
>  	{ .compatible = "st,stm32-dcmi"},
>  	{ /* end node */ },
> @@ -916,7 +938,13 @@ static int dcmi_open(struct file *file)
>  	if (ret < 0 && ret != -ENOIOCTLCMD)
>  		goto fh_rel;
>  
> +	ret = dcmi_set_default_fmt(dcmi);
> +	if (ret)
> +		goto power_off;
> +
>  	ret = dcmi_set_fmt(dcmi, &dcmi->fmt);
> +
> +power_off:
>  	if (ret)
>  		v4l2_subdev_call(sd, core, s_power, 0);
>  fh_rel:
> @@ -991,27 +1019,6 @@ static int dcmi_release(struct file *file)
>  	.read		= vb2_fop_read,
>  };
>  
> -static int dcmi_set_default_fmt(struct stm32_dcmi *dcmi)
> -{
> -	struct v4l2_format f = {
> -		.type = V4L2_BUF_TYPE_VIDEO_CAPTURE,
> -		.fmt.pix = {
> -			.width		= CIF_WIDTH,
> -			.height		= CIF_HEIGHT,
> -			.field		= V4L2_FIELD_NONE,
> -			.pixelformat	= dcmi->sd_formats[0]->fourcc,
> -		},
> -	};
> -	int ret;
> -
> -	ret = dcmi_try_fmt(dcmi, &f, NULL);
> -	if (ret)
> -		return ret;
> -	dcmi->sd_format = dcmi->sd_formats[0];
> -	dcmi->fmt = f;
> -	return 0;
> -}
> -
>  static const struct dcmi_format dcmi_formats[] = {
>  	{
>  		.fourcc = V4L2_PIX_FMT_RGB565,
>